In the processing of semiconductors, planar structuring elements can be produced on or in substrates by depositing layers and subsequently structuring them, or through processes of etching the bulk material. This technology is known as planar technology.
An aspect of planar technology relates to the production of non-planar structures such as oblique or curved surfaces.
U.S. Pat. No. 5,174,587 describes an oblique etching process in which a photoresist layer is made to flow under a predetermined high temperature in order to form oblique photoresist edges that are then, in a subsequent etching step, etched together with the substrate situated thereunder to form oblique planes.
U.S. Patent Application Publication No. 2005/0257709 A1 describes a method in which optical or diffractive elements on a substrate are covered by a layer that is to be structured, and through a masking layer a region of the layer to be structured over the optical elements is exposed. The optical elements reflect the radiation and cast the light at an angle into a further region of the layer that is to be structured, so that obliquely exposed regions are formed.
U.S. Patent Application Publication No. 2002/0135717 A1 describes methods by which oblique surfaces can be fashioned by depositing organic layers over structured substrate elements.
In addition, lithographic methods are available, for example gray-tone or half-tone lithography, that can be used to produce regions in a substrate that are structured to different extents. The masking layers here are relatively thin, and the masking material can be selected such that during the etching only a slight abrasion occurs, for example via a high etching selectivity of the masking material relative to the substrate to be etched.
In particular for the covering of microelectromechanical systems having micromirrors by a window, oblique surfaces are often required in order to keep scattered light and undesired reflections of the light source away from the micromirror or from the projected image.
U.S. Patent Application Publication Nos. 2006/1076539 A1 and 2007/0024549 A1 describe methods in which pre-formed coverings having oblique surfaces are placed over micromirror arrays.
German Patent No. DE 10 2008 012 384 A1 describes methods for producing a glass wafer having beveled surfaces that can act as coverings for micromirrors.
However, in order to implement a large-scale production method for oblique and/or curved surfaces in a planar technology environment, it is desirable to provide more efficient and more economical methods.